1. Technical Field
The disclosure relates to a light guide module and a backlighting module. More particularly, the disclosure relates to light guide module and a backlighting module both with a gradient index lens.
2. Background
Traditionally, an edge-lit backlighting module comprises a light guide plate and a light source. The light source is located at a side of the light guide plate. When light emitted from the light source enters the light guide plate, the light is guided toward a display panel evenly, and an illumination of the display panel is enhanced.
Since a new design concept has been established to make electronic devices (such as tablet computers, laptop computers) and display screens of the electronic devices become smaller in size and lighter in weight, the light guide plate of the edge-lit backlighting module has developed to be miniaturized accordingly. However, when a light incident surface of the light guide plate is smaller than a light emitting surface of the light source, the light incident surface of the light guide plate cannot totally covers the light emitting surface of the light source. Thus, it causes light leakage and reduces the utilization efficiency of the light source.
To solve the above-mentioned problem, the shape of a part of the light guide plate is trapezoidal, i.e wedged-shaped, wherein the light guide plate has two opposite ends, and the end of the light guide plate closer to the light source is thicker than the other end of the light guide plate. Accordingly, an inclined plane of the light guide plate can guide the light back to the light guide plate, and then the light can be output from a light output surface of the light guide plate, to avoid light leakage. However, when the slope of the inclined plane of the light guide plate is too steep, the light guide plate cannot guide the light well to avoid light leakage. When the slope of the inclined plane of the light guide plate is too gentle, a large portion of the light guide plate where cannot output the light becomes larger, such that the manufacturing cost of the light guide plate is increased.
Therefore, manufacturers try to develop a new light guide module in order to avoid light leakage and improve the efficiency of light receiving of the light guide plate relative to the light source.